When it comes to taking someone's temperature, use the method that will give the most accurate reading. For babies and children under five years of age, taking a rectal temperature is most accurate. For older children and adults, taking an oral temperature is perfectly fine. As an alternative for people of any age, you may take an axillary (armpit) temperature, but this method is not as accurate as the others and should not be relied upon if you're worried the person has a fever.

Choose a Method

Oral: For adults or older children. Infants cannot hold the thermometer in their mouth.

Armpit: Too inaccurate for use on infants. Use for a quick check, then switch to another method if result is above 99 °F (37 °C).

Steps

Method1

Taking Oral Temperature

1

Use a multi-use or oral digital thermometer. Some digital thermometers are designed to be used either rectally, orally or in the armpit, while others are designed to be used specifically in the mouth. Either type of thermometer will give an accurate reading. You can find digital thermometers in the drugstore.

If you have an old glass thermometer, dispose of it instead of using it to take a temperature. Glass thermometers are considered unsafe now because they contain mercury, which is poisonous to the touch.

2

Wait 20 minutes after bathing. A warm bath or could affect the child's body temperature, so wait a good 20 minutes to make sure you get the most accurate possible reading.[1]

3

Prepare the tip of the thermometer. Clean it with rubbing alcohol soap and warm water, then rinse it with cool water and dry it thoroughly. [2]

4

Turn on the thermometer and insert it under the tongue. Make sure the tip is completely in the mouth and under the tongue, not up near the lips. The person's tongue should completely cover the tip of the thermometer.

If you're taking your child's temperature, either hold the thermometer in place or instruct your child to do so.

Try to move the thermometer as little as possible.

5

Remove the thermometer when it beeps. Look at the digital display to determine whether the person has a fever. Any temperature above 100.4 °F (38.0 °C) is considered a fever, but going to the doctor right away isn't necessary unless the fever is above a certain temperature:

If the child is over 5 months old, call the doctor for a fever 101 °F (38 °C) or higher.[3]

If the person with the fever is an adult, call the doctor if it's 104 °F (40 °C) or higher.

6

Wash the thermometer before putting it away. Use warm, soapy water and dry it thoroughly before putting it away for next time.

Method2

Taking Axillary (Armpit) Temperature

1

Use a multi-use digital thermometer. Look for a digital thermometer designed to be used either rectally, orally or in the armpit. This way you can take the axillary temperature first, and if a high temperature is indicated, you can try a different method as well.

If you have an old glass thermometer, dispose of it instead of using it to take a temperature. Glass thermometers are considered unsafe now because they contain mercury, which is poisonous to the touch.

2

Turn on the thermometer and place it in the armpit. Lift the arm, insert the thermometer, then lower the arm so the tip of the thermometer is snug in the middle of the armpit. The entire tip should be covered.[4]

3

Remove the thermometer when it beeps. Look at the digital display to determine whether the person has a fever. Any temperature above 100.4 °F (38.0 °C) is considered a fever, but going to the doctor right away isn't necessary unless the fever is above a certain temperature:

If the child is over 5 months old, call the doctor for a fever 101 °F (38 °C) or higher.

If the person with the fever is an adult, call the doctor if it's 104 °F (40 °C) or higher.

4

Wash the thermometer before putting it away. Use warm, soapy water and dry it thoroughly before putting it away for next time.

Method3

Taking Rectal Temperature

1

Use a multi-use or rectal digital thermometer. Some digital thermometers are designed to be used either rectally, orally or in the armpit, while others are designed to be used specifically in the rectum. Either type of thermometer will give an accurate reading. You can find digital thermometers in the drugstore.

Look for a model that has a wide handle and a sip that can't be inserted too far into the rectum. This will make the process easier and help prevent you from inserting the thermometer too far.[5]

If you have an old glass thermometer, dispose of it instead of using it to take a temperature. Glass thermometers are considered unsafe now because they contain mercury, which is poisonous to the tough.

2

Wait 20 minutes after bathing or swaddling. A warm bath or a snug swaddling session could affect the child's body temperature, so wait a good 20 minutes to make sure you get the most accurate possible reading.[6]

3

Prepare the tip of the thermometer. Clean it with rubbing alcohol soap and warm water, then rinse it with cool water and dry it thoroughly. Cover the tip with petroleum jelly to make it easier to insert.[7]

4

Position the child comfortably. Place the child either tummy down across your lap, or tummy up on a firm surface. Choose the position that's most comfortable for the child and makes it easiest for you to access the rectum.

5

Turn on the thermometer. Most digital thermometers have a clearly labeled button you press to power on the device. Allow a moment or two for it to get set to take the temperature.

6

Hold the child's buttocks apart and gently insert the thermometer. Use one hand to hold the child's buttocks apart and the other to insert the thermometer about three quarters of an inch to once inch inside. Stop if any resistance is felt.[8]

Keep the thermometer in place by holding it between your first and middle fingers. Meanwhile, keep your other hand hand firmly but gently on the child's bottom to prevent squirming.

If this question (or a similar one) is answered twice in this section, please click here to let us know.

Tips

Always see a medical provider if concerned about your child's welfare.

Using an electronic ear thermometer or plastic strip type thermometer is not recommended. Neither provide as accurate temperature readings as the digital thermometer.

Use a designated digital thermometer to take rectal temperatures. This helps keep things sanitary.

A low-grade fever is considered 100.4 F while a high-grade fever is considered 104 °F (40 °C). This is a general guideline.

Warnings

Call your medical provider, or go to the emergency room, if a baby 3 months or younger has a rectal temperature of 100.4 F or higher.

Always sanitize thermometers immediately after you use them.

Dispose of old mercury thermometers properly. Even the tiny amount of mercury in a thermometer is enough to do much environmental harm if it is released. Contact your city about hazardous waste disposal.